On Tue, Feb 15, 2022 at 02:28:24PM +0100, Thomas Huth wrote: > On 11/02/2022 17.48, Thomas Huth wrote: > > On 11/02/2022 17.14, Eric Blake wrote: > > > On Tue, Feb 08, 2022 at 03:52:19PM +0100, Thomas Huth wrote: > > > > > > The current code with $SED has been introduced almost three years > > > > > > ago already... > > > > > > > > > > > > > Can’t we just do `alias sed=gsed`? > > > > > > > > > > > > Maybe ... but let's ask Philippe and Kevin first, who Signed-off > > > > > > commit bde36af1ab4f476 that introduced the current way with $SED: > > > > > > What's your opinion about this? > > > > > > > > > > This commit was to have check-block working on the OpenBSD VM image. > > > > > > > > Sure. The question was whether using an alias as suggested by Hanna > > > > would be > > > > nicer instead of using $SED ? > > > > > > Scripting with aliases becomes a nightmare to debug, since it is > > > relatively uncommon. In particular, in bash, you have to explicitly > > > opt in to using aliases (contrary to POSIX sh where aliases are > > > available to scripts at startup). > > > > shopt -s expand_aliases > > ... as I just learnt the hard way ;-) > > > > > Using $SED everywhere may require > > > more hunting, but it is more obvious when reading a test that "oh > > > yeah, I might be using extensions that the default 'sed' can't > > > support" than a script that blindly uses 'sed' and depends on it > > > aliasing to a more-capable sed at a distance. > > > > > > The other question is how many GNU sed features are we actually > > > depending on? Which tests break if we have BSD sed or busybox sed? > > > Can we rewrite those sed scripts to avoid GNU extensions? But > > > auditing for s/sed/$SED/ seems easier than auditing for which > > > non-portable sed extensions we depend on. > > > > The most obvious part are the filter functions in common.filter - we're > > using "-r" here that is not part of the POSIX sed as far as I can see. > > Now that I stepped through the list, the other major part that is failing on > non-GNU seds are the statements that use "\r" or "\n" or "\e" to replace > special characters. That seems to be a non-POSIX extension, too. > > But for running with Alpine, there is also the additional problems that the > libc uses slightly different error strings, e.g. "I/O error" instead of > "Input/output error", see e.g.: > > https://gitlab.com/thuth/qemu/-/jobs/2094869856 > > Maybe it could be fixed with some extensions to the filters, but I'm not > sure whether we really want to go down that road...?
AFAIK, errno strings are not standardized by POSIX, so I presume this problem will apply to running I/O tests on any non-Linux system too. With this in mind I think we should consider what a portable solution looks like. We can't simply match the Alpine strings and turn them into GLibC strings, as that does nothing to help portability on *BSD, macOS, Windows, etc. We would need to figure out how to blank out arbitrary input error message strings. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
